Using Quick Georeference

An image can be georeferenced using one reference point and the pixel or image size, two reference points, copy from an existing document or copy from a file. Certain conditions and information are needed using this approach.

To start, click the Quick Georeference button in the Georeference dialog box. Choose one of the four Quick Georeference options:

• By Two Reference Points (North/South aligned)
• By Tie Point (North/South aligned)
• Copy From Document (same size/reference)
• Copy From File (same size/reference)

By Two Reference Points (North/South aligned)

Requirements to use two points:

• Two reference point coordinates are known, however these points must not contain the same coordinates in either the pixel (X/Y) or world (WX/WY) values.
• The image is not rotated (image is North/South aligned).

Using this method changes the mode back to Standard. In this process, the four corner coordinates of the image are generated to define the referencing. Points that were not chosen to be used in the georeferencing are discarded. No dialog box opens for this method, the changes are implemented immediately.

 Placement of the two reference points used for Quick Georeference should be far apart to achieve a better reference.

By Tie point (North/South aligned)

Requirements to use one tie point:

• One reference point coordinate is known (pixel and world location).
• The image is not rotated (image is North/South aligned).
• The pixel size or image size in world units is known.

Pixel size or image size must be in world units (geodetic or projected). Change the method to enter either pixel size or image size.

Quick georeference by one tie point and existing document uses a georeferenced image as the source to georeference an unreferenced image (as long as the second condition above is met). An existing document must have the same coordinate system and pixel size but does not have to contain the geographic extents of the image being georeferenced. Select By tie point and existing document from the drop-down list to use this method.

Copy From Document (same size/reference)

This method copies all the geographic details from a georeferenced image into an unreferenced image. An open georeferenced document must contain the same geographic details like the image being georeferenced:

• Geographic extents (top left and bottom right corner coordinates)
• Image size
• Pixel size
• Rotation

 When Quick Georeference is used, the precision needs to be set to the longest pixel value. When the precision is less than the pixel value, the pixel value may be modified. When it is modified, the image will not be able to be mosaicked with other images of the same pixel value.

Copy From File (same size/reference)

This method copies all details from a georeferenced image to the current image. This is similar to the Copy From Document method, except that the source document does not have to be opened in Adobe Photoshop. Choose a supported file format and appropriate reference file to use for georeferencing and click Open to load its control points and coordinate system information.